A radiation imaging apparatus as an example of an imaging apparatus converts incident energy, such as a radiation or a light incident to a conversion element, such as photoelectric conversion elements, into an electric charge, and reads out, for each pixel, an electric signal based on the electric charge. Such an electric signal is hereinafter referred to as a pixel signal, and a collection of one image worth of pixel signals is referred to as an image signal. The read out image signal is used as data through various types of signal processing, such as digital processing, or printed or displayed as image data, which is a collection of one image worth of data. The image signal derived from the conversion element is subject to an offset correction especially when the signal is used as image data. The offset correction is performed by subtracting offset image data from the image data, for example. The offset image data is a collection of one image worth of offset data based on electric signals based on the electric charge caused by dark current accumulated on the conversion element when no radiation or light has irradiated the conversion element. The electric signal based on the electric charge caused by dark current accumulated on the conversion element when no radiation or light has irradiated the conversion element is referred to as a dark output pixel signal, and a collection of one image worth of dark output pixel signals is referred to as a dark output image signal.
For example, a low-noise offset correction has been proposed in U.S. Patent Application Publication No. 2004/0017891, which described that an offset correction is performed by subtracting from radiation image data, corrected image data including a plurality of offset image data that have been averaged. Hereinafter, in an image generated based on image data (imaging output) acquired from a radiation imaging apparatus, the variation in the output over the entire image is referred to as random noise. Further, the variation in the average output of each pixel group arranged in the perpendicular direction to signal wirings (along driving wirings), among the pixels arranged in a matrix, is referred to as line noise. U.S. Patent Application Publication No. 2003/0190088 described a suitable circuit structure for line noise reduction, in which image processing is performed, which detects whether or not line noise is included in the imaging output based on the acquired image signals, and, if line noise is detected, eliminates a line noise component.